RESUMO
Fusarium foetens is a destructive vascular pathogen on Begonia, mainly on cultivars of Begonia elatior hybrids (Begonia × hiemalis), which has recently been identified in Europe and Northern America (1,3). This Fusarium species has been responsible for severe damage in the begonia flower industry (1) and is listed as an EPPO A2 quarantine pathogen since 2007. In May 2007, wilted potted plants of B. elatior showing chlorotic leaves and basal stem rot were observed in a nursery located in the west of France (La Flèche, Sarthe). Symptomatic foliar and basal stem pieces were plated on a Fusarium semi selective medium, dichloran chloramphenicol peptone agar (DCPA), and on malt agar medium supplemented with 100 ppm chloramphenicol. Homogeneous mycelium of a Fusarium species developed from both types of tissue and on both media, and was transferred to potato dextrose agar (PDA) and to spezieller nährstoffarmer agar (SNA) media for morphological examination. Microscope slides were then prepared by pressing gently a clear self-adhesive tape onto the surface covered by mycelium and sporodochia, which was further stained with lactic acid/methylene blue. Typical multiseptate (often three septa), hyaline, slightly curved Fusarium macroconidia 29.2 to 41.8 (32.5) × 3.6 to 4.5 (4.3) µm were collected in sporodochia. In the aerial mycelium, long and short conidiophores with mono- or polyphialidic cells bearing false heads of ellipsoidal microconidia were observed. In addition, a pungent distinctive odor was produced by the mycelium grown on PDA. These features were consistent with F. foetens (2). To support the diagnosis, total DNA was further extracted from the pure culture and a partial region of the translation elongation 1 (tef1) gene was amplified by PCR using EF1-EF2 primer pair (4). Nucleotide sequence was determined and deposited on GenBank (Accession No. JX298790). Analysis of the sequence by BLAST showed that it was 100% identical with all the available F. foetens sequences, which confirmed our morphological diagnosis. To our knowledge, this is the first official report of F. foetens in France. Since this first detection, F. foetens was again identified in 2010 in another nursery located in the Pays de la Loire on collapsed B. elatior. Approximately 15 to 20% of the Begonia plants showed typical Fusarium wilt symptoms and the infected lots were systematically destroyed. The origin of these infections could not be traced back since the mother plants tested negative. The disease is considered as eradicated in France but causes major economic losses to Begonia growers and marketers in regions where the disease is established (2). References: (1) H. Huvenne et al. Eur. J. Plant Pathol. 131:705, 2011. (2) H. J. Schroers et al. Mycologia 96:393, 2004. (3) X. L. Tian et al. Plant Dis. 94:1261, 2010. (4) D. Geiser. Eur. J. Plant Pathol. 110:473, 2004.
RESUMO
Cylindrocladium buxicola Henricot causes twig blight on Buxus spp., severe defoliation, and eventually death of plants, especially in young seedlings (1). The disease was first observed in the United Kingdom and New Zealand in the 1990s and recently, the fungus was detected in other European countries (1). In November 2006, box blight symptoms were observed in a Buxus sempervirens nursery located in the South West of France (La Reole). Since then, more diseased samples from other French sites, including forestry areas and ornamental garden nurseries, have been received, indicating that this disease is spreading. Symptomatic twig samples were sent for lab analysis and dark brown spots were observed on the leaves, sometimes coalescing to cover the entire leaf surface, with black streaks on the stems. Fungal fruiting structures were observed directly on the leaf surface and were examined with a stereomicroscope. Microscopic slides were then prepared by gently pressing a clear adhesive tape onto the surface covered by mycelium and spores, which was further stained with lactic acid and methyl blue. Cylindrical, straight, biseptate, hyaline conidia, 53.8 to 75.3 (64.4) × 4.4 to 5.2 (4.6) µm, were observed, sterile hyphae with terminal vesicles ended with a pointed apex, and conidiophores were penicilliate; all of those characters were consistent with C. buxicola (2). To support the diagnosis, fruiting structures were plated on malt agar media supplemented with 100 ppm of chloramphenicol. The pure culture obtained showed a whitish mycelium with a tan brown center that was in line with the original description of C. buxicola (2). DNA was extracted from the pure culture and the internal transcribed spacer (ITS) region was amplified by PCR using the ITS1-ITS4 primer pair (4). Nucleotide sequence was determined and deposited on GenBank (Accession No. JQ743502). BLAST analysis of the sequence showed 100% identity with all currently available C. buxicola ITS sequences, which confirmed our morphological diagnosis. To our knowledge, this is the first report of C. buxicola (teleomorph Calonectria pseudonaviculata) in France. The occurrence of this disease in France worries the nursery industry since losses can sometimes be dramatic as seen in United Kingdom, where the disease is widespread (3). References: (1) B. Henricot. The Plantsman 9:153, 2006. (2) B. Henricot and A. Culham. Mycologia 94:980, 2002. (3) B. Henricot et al. Plant Pathol. 49:805, 2000. (4) T. J. White et al. Page 315 in: PCR Protocols: A Guide to Methods and Applications, 1990.
RESUMO
In April 2002, Phytophthora ramorum was associated with twig blight and brown spots on Rhododendron spp. leaves from a nursery in France. The isolate was identified by its morphological characters on V8 agar: slow growth, deciduous and semipapillate sporangia, and abundant production of large chlamydospores (3). The identification was confirmed by ITS rDNA sequencing. During 2002, P. ramorum was also isolated from diseased Viburnum tinus and V. × bodnantense plants exhibiting symptoms of wilting and stem base discoloration. Subsequently, repeated surveys for P. ramorum were carried out in nurseries and areas surrounding nurseries throughout France. Since 2004, a large range of known hosts were investigated in approximately 2,000 nurseries and 200 other sites each year. P. ramorum was detected exclusively in nurseries at 29 locations in 2002, 9 in 2003, 23 in 2004, 17 in 2005, and 19 in 2006. Rhododendron spp. and occasionally V. tinus were the major hosts. In addition, the pathogen was detected for the first time on Pieris japonica in two nurseries in 2005 and on Camellia sp. in one nursery in 2006 from plants exhibiting leaf and twig blight. In both cases, P. ramorum had already been detected on Rhododendron spp. in the same nurseries. Most of the infected plants were found in northwestern France (Bretagne and Pays-de-la-Loire), or came from this region, which is the main rhododendron-growing area in France. In some cases, plants were imported from Belgium or the Netherlands. P. ramorum was also detected in a nursery in soil close to diseased Rhododendron spp. plants and pond water used for irrigation by using a combination of baiting with Rhododendron spp. leaves and PCR assay with species-specific primers (1). Overall, approximately 1% of the investigated nurseries were found positive each year, and this ratio was quite stable from 2004 to 2006. To date, P. ramorum has not been detected outside of nurseries, although many surveys were conducted on the west coast of France where the risk is considered to be high because of a favorable mild and humid climate and the presence of suitable hosts. In addition, 78 isolates of P. ramorum collected between 2002 and 2004 on Rhododendron spp. and V. tinus were found to be of A1 mating type based on pairings with P. cryptogea A1 and A2 mating types (2). References: (1) K. J. Hayden et al. Phytopathology 94:1075, 2004. (2) S. Werres and B. Zielke J. Plant Dis. Prot. 110:129, 2003. (3) S. Werres et al. Mycol. Res. 105:1155, 2001.
